Queen Elizabeth II and a former Irish Republican Army commander have offered each other the hand of peace in a long-awaited encounter symbolizing Northern Ireland’s progress in achieving reconciliation after decades of violence.

Northern Ireland Office officials say the monarch and Martin McGuinness met privately Wednesday inside a Belfast theater during a cross-community arts event. Media were barred from the event, but the two are expected to have a public handshake later.

Experts say McGuinness was the IRA’s chief of staff when the outlawed group assassinated the queen’s cousin, Lord Louis Mountbatten, in 1979.

The IRA renounced violence and disarmed in 2005. Two years later, McGuinness became the senior Catholic in Northern Ireland’s unity government.

McGuinness’ Irish nationalist party, Sinn Fein, had refused all contact with British royals until Wednesday.